Windows provide natural light, fresh air, access and connection to the outside. However, they represent significant sources of wasted energy (heat loss in winter and solar heat gain in summer), which has been estimated to be about 5 Quads annually (i.e., 5% of total energy usage) in the US. With the growing architectural trend of increasing window area, the balancing of the conflicting interests between energy efficiency and aesthetics is becoming more critical.
Electrochromic windows (ECW), with dynamic control of pertinent optical properties to modulate solar radiation, promise significant reduction in energy use while improving human comfort factors. However, the current state-of-the-art ECW technologies are not market viable as they do not meet the requirements in cost, supply, available sizes and device performance. Device performance issues include appearance (e.g., defects), color selection (including matching non-ECW panes and baseline hue in “clear state” yellow), consistency (e.g., pane-to-pane, over long term production), switching speed and long term reliability (>25 yrs).
Thus, there is a need to develop ECWs that have appropriate color, switching speed and long term reliability.